Preform

Abstract

To provide a preform capable of molding a lightweight plastic bottle for heating with excellent heat resistance.SOLUTION: A plastic bottle for heating includes: a mouth part 11 having a support ring 14; a neck part 21 connected to the mouth part 11; a thickness-changing part 22 that is connected to the neck part 21 and whose thickness changes as it decreases in diameter as it moves away from the neck part 21; a body part 23 connected to the thickness-changing part 22 that has an outer diameter smaller than that of the neck part 21 and a substantially uniform thickness; and a bottom part 24 that is provided on the opposite side of the body part 23 from the thickness-changing part 22. A total weight of the neck part 21, the thickness-changing part 22, the body part 23, and the bottom part 24 is greater than 10.0 g and less than 16.4 g, a body thickness T3 of the body part 23 is greater than 2.7 mm, and when a thickness of the thinnest tip of the bottom part 24 is defined as a bottom thickness T5, a value of the bottom thickness T5 / the body thickness T3 is greater than 71%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] SUMMARY This disclosure relates to preforms for blow molded plastic bottles for heating. [Background technology]

[0002] Conventionally, plastic bottles have been produced by biaxially stretching and blow molding a resin preform produced by injection molding or the like. In addition, in consideration of the environment, it is desired to reduce the amount of plastic material used in plastic bottles and to make the plastic bottles lighter.

[0003] In addition, during the winter season and other times, beverages filled in plastic bottles are sometimes warmed by a heating device called a bottle warmer at stores before being sold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-75421 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the thickness of a conventional preform is simply reduced in order to reduce the weight of the plastic bottle, there is a concern that the heat resistance of the plastic bottle produced by blow molding will deteriorate. For example, if the resin is not properly stretched during blow molding, the resin may whiten (crystallize) when heated. In addition, when a beverage filled in a plastic bottle with low heat resistance is heated by a bottle warmer, a phenomenon called buckling may occur, in which the shape of the bottom part is deformed so as to protrude outward due to an increase in internal pressure. In addition, deformation due to heating may occur not only in the bottom part, but also in, for example, the vicinity of the base of the mouth part of the plastic bottle.

[0006] An object of the present disclosure is to provide a preform capable of molding a plastic bottle for heating that is lightweight and has good heat resistance. [Means for solving the problem]

[0007] The present disclosure solves the above problems by the following solving means. Note that, for ease of understanding, the following description will be given with reference symbols corresponding to the embodiments of the present disclosure, but the present disclosure is not limited thereto.

[0008] The first disclosure relates to a preform (10) for a plastic bottle (40, 50) for heating, comprising: a mouth portion (11) having a support ring (14); a neck portion (21) connected to the mouth portion (11); a thickness-changing portion (22) connected to the neck portion (21) and having a thickness-changing portion (22) that decreases in diameter as it moves away from the neck portion (21); a body portion (23) connected to the thickness-changing portion (22) that has an outer diameter smaller than that of the neck portion (21) and has a substantially uniform thickness; and a bottom portion (24) provided on the side of the neck portion (21), wherein the total weight of the neck portion (21), the thickness changing portion (22), the body portion (23) and the bottom portion (24) is greater than 10.0 g and less than 16.4 g, a body thickness (T3) that is the thickness of the body portion (23) is greater than 2.7 mm, and when the bottom thickness (T5) is the thickness of the thinnest tip of the bottom portion (24), a value of bottom thickness (T5) / body thickness (T3) is greater than 71%.

[0009] The second disclosure is the preform (10) according to the first disclosure, wherein the length from the tip of the bottom portion (24) to the boundary between the neck portion (21) and the mouth portion (11) is greater than 55 mm.

[0010] A third disclosure is the preform (10) according to the first or second disclosure, which is made of polyethylene terephthalate resin.

[0011] A fourth disclosure is the preform (10) according to the third disclosure, further comprising an aluminum compound as a polymerization catalyst for the polyethylene terephthalate resin. Effect of the Invention

[0012] According to the present disclosure, it is possible to provide a preform capable of molding a plastic bottle for heating that is lightweight and has good heat resistance properties. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a front view of an embodiment of a preform according to the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view taken along the central axis of the preform. [Diagram 3] 1A to 1C are diagrams showing examples of plastic bottles that can be produced using the preform of this embodiment. [Figure 4] FIG. 1 is a perspective view of an example of a plastic bottle that can be produced using the preform of this embodiment, as viewed from the bottom side. [Diagram 5] FIG. 13 is a diagram showing a list of evaluation items. [Figure 6] FIG. 13 is a diagram summarizing the evaluation results. [Figure 7] 1 is a photograph comparing the bottom of a bottle obtained by blow molding a 280 ml bottle using the preform of Example 1 with the bottom of a bottle obtained by blow molding a 280 ml bottle using the preform of Comparative Example 1. [Figure 8] FIG. 1 is a diagram showing the evaluation results of a polymerization catalyst for a polyethylene terephthalate resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the best mode for carrying out the present disclosure will be described with reference to the drawings.

[0015] (Embodiment) FIG. 1 is a front view illustrating an embodiment of a preform according to the present disclosure. FIG. 2 is a cross-sectional view taken along the central axis of the preform. First, an overview of the preform of the present disclosure will be described with reference to FIGS. In the following description, specific numerical values, shapes, materials, etc. are given, but these can be changed as appropriate. In the following description, "upper" and "lower" refer to the upper and lower sides in a state in which the mouth 11 of the preform 10 faces vertically upward and the bottom 24 of the preform 10 faces vertically downward (the state shown in Figs. 1 and 2). In addition, the "central axis CL" of the preform 10 refers to the central axis of the cylinder that constitutes the inner surface of the mouth 11 of the preform 10.

[0016] In this specification, the term "height direction" refers to the direction along the central axis CL of the preform 10. The term "circumferential direction" refers to the circumferential direction of a circle centered on the central axis CL of the preform 10. The term "horizontal cross section" refers to a cross section cut along a plane perpendicular to the central axis CL of the preform 10. The term "vertical cross section" refers to a cross section cut along a plane including the central axis CL of the preform 10.

[0017] The preform 10 for a plastic bottle shown in Figures 1 and 2 has a mouth portion 11 having an opening 15, and further has a neck portion 21, a thickness-changing portion 22, a body portion 23, and a bottom portion 24, which are connected in this order downward from the mouth portion 11.

[0018] The mouth portion 11 has a cylindrical mouth body 12, a threaded portion 13 provided on the outer periphery of the mouth body 12, and a support ring 14 provided below the threaded portion 13. The threaded portion 13 is for screwing a cap (not shown) after the preform 10 is biaxially stretched and blow molded to produce a plastic bottle 40 (FIGS. 3 and 4). The mouth body 12 has a length L1 in the height direction, an outer diameter D1, and an inner diameter D2. The outer diameter D1 of the mouth body 12 may be 20 mm or more and 40 mm or less, and the inner diameter D2 of the mouth body 12 may be 15 mm or more and 30 mm or less. The length L1 in the height direction of the mouth portion 11 may be, for example, 9 mm or more and 26 mm or less.

[0019] The support ring 14 is provided at the bottom of the mouth portion 11 and protrudes in an annular shape over the entire circumference. A neck portion 21 is connected to the bottom of the support ring 14.

[0020] The neck 21 is connected to the lower part of the support ring 14 and has a length L2 in the height direction. When viewed in a cross-sectional view cut along the central axis CL, the outer diameter side of the neck 21 is approximately parallel to the central axis CL. The neck 21 is generally approximately cylindrical in shape, and has an outer surface 21a and an inner surface 21b, an outer diameter D3, an inner diameter D4, and a wall thickness T1. The inner diameter D4 of the neck 21 may be approximately the same as the inner diameter D2 of the mouth body 12 described above. The wall thickness T1 of the neck 21 refers to the wall thickness directly below the support ring 14. Note that the neck 21 may have a substantially uniform wall thickness as the wall thickness T1 over the entire height direction, or the wall thickness may vary. Note that when the preform 10 is produced by injection molding or the like, the inner diameter D4 may be made slightly smaller than the inner diameter D2 in order to provide a draft angle for making it easier to remove from the mold.

[0021] The thickness-changing portion 22 is connected to the lower part of the neck portion 21, and has a shape in which the thickness changes while gradually decreasing in diameter from the neck portion 21 side toward the body portion 23 side (as it moves away from the neck portion 21). Specifically, the thickness-changing portion 22 has gradually smaller outer and inner diameters and gradually changes in thickness as it moves away from the neck portion 21. The thickness-changing portion 22 is in the shape of a substantially truncated cone cylinder, and has an outer surface 22a and an inner surface 22b.

[0022] The length L3 in the height direction of the thickness changing portion 22 is, for example, 10 mm or more and 16 mm or less. The horizontal cross section of the thickness changing portion 22 may be circular over the entire height direction. The outer surface 22a of the thickness changing portion 22 has an outer diameter D5 that changes along the height direction, and the inner surface 22b of the thickness changing portion 22 has an inner diameter D6 that changes along the height direction. The outer diameter D5 and the inner diameter D6 of the thickness changing portion 22 each gradually become narrower from the neck portion 21 side toward the body portion 23 side. The outer surface 22a and the inner surface 22b of the thickness changing portion 22 each incline with respect to the central axis CL of the preform 10.

[0023] Furthermore, the thickness T2 of the thickness changing portion 22 gradually changes from the neck portion 21 side toward the body portion 23 side. That is, the thickness T2 of the thickness changing portion 22 changes such that the body thickness T3, which is the thickness at the body portion 23, is thicker than the thickness T1 at the neck portion 21. In this manner, the thickness T2 of the thickness changing portion 22 gradually becomes thicker from the neck portion 21 side toward the body portion 23 side, but there may be some parts where the thickness is uniform and some parts where the thickness changes to be thinner.

[0024] The body 23 is connected to the lower part of the thickness changing part 22 and is a part formed in a cylindrical shape. When viewed in a cross-sectional view cut along the central axis CL, the outer diameter side of the body 23 is approximately parallel to the central axis CL. The body 23 has an outer surface 23a, an inner surface 23b, a length L4 in the height direction, an outer diameter D7, and an inner diameter D8. The outer surface 23a of the body 23 is a cylindrical surface approximately parallel to the central axis CL of the preform 10. The inner surface 23b is also a cylindrical surface approximately parallel to the central axis CL of the preform 10, but the vicinity of the thickness changing part 22 and the vicinity of the bottom 24 of the inner surface 23b do not have to be a cylindrical surface approximately parallel to the central axis CL. The horizontal cross section of the body 23 is circular throughout the entire height direction. Therefore, the body thickness T3, which is the thickness of the body 23, is approximately uniform. Here, the reason why the thickness is "substantially" uniform is that the outer surface 23a and the inner surface 23b of the body 23 may have a draft of 0.1° or more and 0.5° or less, and the thickness may vary slightly depending on how the draft of the outer surface 23a and the inner surface 23b is set, and the thickness change part 22 of the inner surface 23b and the bottom 24 may not be a cylindrical surface substantially parallel to the central axis CL. The draft refers to the angle between the central axis CL and the outer surface 23a or the inner surface 23b. By providing this draft, the outer diameter D7 and the inner diameter D8 may be configured to be slightly thinner on the bottom 24 side than on the mouth 11 side. In addition, if the difference between the thickness of the maximum thickness part where the thickness is the maximum and the thickness of the minimum thickness part where the thickness is the minimum is 0.1 mm or less, the thickness can be considered to be substantially uniform.

[0025] Here, it is desirable that the inside diameter D8 of the body 23 is φ12 mm or more at its narrowest point. When molding a plastic bottle, which will be described later, using the preform 10 by the biaxial stretch blow molding method, the preform is heated, stretched in the axial direction with a stretch rod, and then inflated with high-pressure air. At this time, if the inside diameter D8 of the body 23 is less than φ12 mm, there is a risk that the stretch rod will interfere with the inner wall of the preform when the preform is stretched with the stretch rod.

[0026] The bottom 24 is connected to the lower part of the body 23 and is provided so as to close the opening of the cylindrical body 23. The bottom 24 has an outer surface 24a and an inner surface 24b. The bottom 24 is generally semispherical. In a vertical cross section, the outer surface 24a of the bottom 24 is generally semicircular, but the outer surface 24a of the bottom 24 may be a curved shape including a non-circular portion. Similarly, in a vertical cross section, the inner surface 24b of the bottom 24 is generally semicircular, but a part of the inner surface 24b of the bottom 24 may be a curved shape including a non-circular portion. In a vertical cross section, the center O1 of the semicircle that constitutes the outer surface 24a of the bottom 24 exists on the central axis CL. In addition, the center O2 of the semicircle that constitutes the inner surface 24b of the bottom 24 exists on the central axis CL. Note that the center O1 of the semicircle that constitutes the outer surface 24a of the bottom 24 exists on the mouth portion 11 side of the center O2 of the semicircle that constitutes the inner surface 24b of the bottom 24. Therefore, the thickness T6 of the bottom portion 24 is the thickest at the boundary with the body portion 23 and gradually becomes thinner toward the tip (lower end) of the bottom portion 24, with the bottom thickness T5 at the tip of the bottom portion 24 being the thinnest. Furthermore, at the lowest end (tip) of the bottom portion 24, a gate G is formed for pouring resin when the preform 10 is injection molded, but this gate G is cut off at the tip of the bottom portion 24, leaving a cut-off mark of the gate G. For the sake of explanation, the cut-off gate G that does not actually exist is shown in FIG.

[0027] The radius of curvature R1 of the hemisphere that forms the outer surface 24a of the bottom portion 24 is half the outer diameter D7 of the body portion 23. Similarly, the radius of curvature R2 of the hemisphere that forms the inner surface 24b of the bottom portion 24 is half the inner diameter D8 of the body portion 23. When the bottom portion 24 has a generally hemispherical shape as a whole, the length L5 of the bottom portion 24 in the height direction is the radius of the hemispherical shape of the outer surface 24a, that is, half the outer diameter D7 of the body portion 23. The horizontal cross section of the bottom 24 is circular throughout its height.

[0028] Here, the area including the neck portion 21, the thickness changing portion 22, the body portion 23, and the bottom portion 24 is also referred to as the deformed portion 20. During blow molding, this deformed portion 20 is mainly deformed. The total length in the height direction of the neck portion 21, the thickness changing portion 22, the body portion 23, and the bottom portion 24, i.e., the length from the tip of the bottom portion 24 to the boundary between the neck portion 21 and the mouth portion 11 in the preform 10 (the length in the height direction of the deformed portion 20) is L6. The length L6 of the deformed portion 20 is the sum of the above-mentioned lengths L2, L3, L4, and L5 (L6=L2+L3+L4+L5). It is desirable that the length L6 of the deformed portion 20 is greater than 55 mm. The reason for this will be described later. The overall length of the preform 10 is L7, which is the sum of the lengths L6 and L1 of the above-mentioned deformed portion 20 (L7=L1+L6). The overall length L7 of the preform 10 may be 76 mm or more and 113 mm or less.

[0029] As the main material of the preform 10, it is preferable to use a thermoplastic resin, particularly PE (polyethylene), PP (polypropylene), PET (polyethylene terephthalate), or PEN (polyethylene naphthalate). It is also possible to use a biomass-based plastic derived from plants, such as PLA (polylactic acid). Alternatively, a resin obtained by blending the above-mentioned various resins may be used. In the case of PET, it may be a mechanically recycled material or a chemically recycled material. It may also be PET or PEF (polyethylene furanoate) manufactured using raw materials derived from plants. The preform 10 may also be formed as a multi-layered molded preform having two or more layers. That is, the preform 10 may be formed by injection molding as a preform having three or more layers, for example, with the intermediate layer being a resin (intermediate layer) having gas barrier properties, such as MXD6, MXD6 + fatty acid salt, PGA (polyglycolic acid), EVOH (ethylene vinyl alcohol copolymer), or PEN (polyethylene naphthalate).

[0030] When the preform is made of a polyester resin such as PET or PEN, the polyester may be selected from antimony-catalyzed polyester, manganese-catalyzed polyester, titanium-catalyzed polyester, aluminum-catalyzed polyester, lithium-catalyzed polyester, and germanium-catalyzed polyester. In this specification, for example, antimony-catalyzed polyester means polyester in which an antimony catalyst is used as a polymerization catalyst during the production of the polyester. Therefore, the polyesters listed above mean polyesters in which each catalyst is used as a polymerization catalyst.

[0031] Examples of antimony catalysts include antimony trioxide, antimony pentoxide, antimony acetate, triphenylantimony, and antimony glycol.

[0032] Examples of the manganese catalyst include fatty acid manganese salts such as manganese acetate, manganese carbonate, manganese chloride, manganese acetylacetonate salts, and manganese hydroxide.

[0033] Examples of the titanium catalyst include titanium alkoxides such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and tetrabenzyl titanate; titanium oxides obtained by hydrolysis of titanium alkoxides; titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanic acid-aluminum hydroxide mixtures, titanium chloride, titanium chloride-aluminum chloride mixtures, titanium bromide, titanium fluoride, potassium hexafluorotitanate, cobalt hexafluorotitanate, manganese hexafluorotitanate, ammonium hexafluorotitanate, and titanium acetylacetonate.

[0034] Examples of aluminum catalysts include aluminum trisacetylacetate, aluminum monoacetylacetonate bis(ethylacetoacetate), and ethylacetoacetate aluminum diisopropylate.

[0035] Examples of the lithium catalyst include ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and phenyllithium.

[0036] Examples of germanium catalysts include germanium dioxide, germanium tetroxide, germanium tetramethoxide, germanium tetraethoxide, germanium tetrapropoxide, germanium tetrabutoxide, germanium tetrapentoxide, and germanium tetrahexoxide. Among these catalysts, an aluminum catalyst is preferable, as shown in FIG. 8 described later.

[0037] Next, an example of a plastic bottle that can be produced by biaxially stretching and blow molding the preform 10 of this embodiment will be described with reference to Figs. 3A and 3B are diagrams showing a first example of a plastic bottle that can be produced using the preform of this embodiment, in which Fig. 3(a) is a front view and Fig. 3(b) is a cross-sectional view of the bottom. FIG. 4 is a perspective view, seen from the bottom side, of a first example of a plastic bottle that can be produced using the preform of this embodiment.

[0038] The plastic bottle 40 shown in Figs. 3 and 4 has a capacity of 280 ml, a total height not including a lid (not shown) of 132 mm, and a maximum body diameter of φ65 mm. Plastic bottle 40 has a mouth 41 and a body 42 provided below mouth 41. Body 42 is further composed of a shoulder 42a, a body 42b, and a bottom 42c. A neck 45 is formed between the lower part of support ring 47 of mouth 41 and the upper part of shoulder 42a.

[0039] The neck portion 45 of the plastic bottle 40 is substantially cylindrical in shape and extends substantially linearly downward from the support ring 47, where the diameter of the neck portion 45 expands to form a shoulder portion 42a. Furthermore, a threaded portion 46 (corresponding to the threaded portion 13 of the preform 10 described above) for screwing a cap is provided on the outer periphery of the mouth portion 41, and an outwardly protruding annular support ring 47 (corresponding to the support ring 14 of the preform 10 described above) is provided on the outer periphery of the mouth portion 41 below the threaded portion 46.

[0040] The body 42b is generally cylindrical, and has a plurality of circumferential grooves 43 recessed inward around it. When the plastic bottle is heated and the internal pressure rises, the body 42b expands vertically due to the circumferential grooves 43. The horizontal cross section of the body 42b is generally circular. Furthermore, the shoulder 42a is generally truncated cone, and the horizontal cross section of the shoulder 42a is generally circular, with the area gradually increasing from the neck 45 side toward the body 42b side.

[0041] Bottom 42c is recessed toward the inside of plastic bottle 40 in a shape basically based on a truncated cone shape, and is provided with multiple bulges 42d that bulge outward (toward the bottom of the bottle) beyond truncated cone surface 42e to reinforce bottom 42c. Note that Fig. 3(b) shows a cross section cut at truncated cone surface 42e and a cross section cut at bulge 42d on the left and right of the center line, respectively. The center of the bottom portion 42c is a flat surface 42f, and a trace (not shown) of the gate G of the preform 10 remains near the center of this flat surface 42f.

[0042] Next, a method for manufacturing the plastic bottle 40 having such a structure will be described. First, the preform 10 shown in Fig. 1 and Fig. 2 is prepared. In this case, pellets made of a thermoplastic resin such as PET (polyethylene terephthalate) are put into an injection molding machine, and the pellets are heated and melted by the injection molding machine. The pellets then become molten plastic and are injected into an injection molding die having an internal shape corresponding to the preform 10. After a predetermined time has passed, the molten plastic hardens in the injection molding die, and the preform 10 is formed. Then, the injection molding die is separated, and the preform 10 shown in Fig. 1 and Fig. 2 is taken out from the injection molding die. Note that the production of the preform 10 is not limited to the injection molding method, and other molding methods such as compression molding may also be used.

[0043] Next, the preform 10 is heated by a heating device. At this time, the preform 10 is heated uniformly in the circumferential direction by the heating device while rotating. The heating temperature of the preform 10 in this heating step may be, for example, 90°C to 130°C.

[0044] Next, the preform 10 heated by the heating device is sent to a blow molding die, and a plastic bottle 40 is molded using this blow molding die. In this case, the blow molding die is composed of a pair of body molds and a bottom mold, which are separated from each other. The preform 10 is placed in these molds. Next, the preform 10 is stretched in the longitudinal direction by a stretch rod (not shown), and air is forced into the preform 10, and the preform 10 is subjected to biaxial stretch blow molding.

[0045] Through the above steps, a plastic bottle 40 is obtained from the preform 10 in the blow molding die. During this time, the temperature of the body die is adjusted to 20°C to 75°C, and the temperature of the bottom die is adjusted to 8°C to 20°C. During this time, the preform 10 is expanded in the blow molding die and shaped into a shape corresponding to the inner surface of the blow molding die. Through this type of blow molding, a plastic bottle 40 as shown in Figs. 3 and 4 is obtained.

[0046] (Suitable form of preform) Next, a suitable form of the preform will be described by comparing specific examples of the preform with comparative examples.

[0047] Here, various evaluations were carried out with the aim of being able to produce a plastic bottle 40 (hereinafter also simply referred to as a "bottle") shown in Figures 3 and 4 using the preform 10. In addition, the produced plastic bottle 40 was also evaluated for having sufficient characteristics to be usable as a plastic bottle for heating. FIG. 5 is a diagram showing a list of evaluation items. The evaluation items shown in FIG. 5 will be explained item by item.

[0048] (Evaluation of preform thickness deviation) To evaluate the thickness unevenness of the preform, the thickness of the body was measured and the difference between the thickest and thinnest points was evaluated. The measurement for this evaluation was performed in an environment of 22°C. As a result of this evaluation, if the difference between the thickest and thinnest points was 0.05 mm or less, it was evaluated as ◯ (evaluated as usable, the same applies below), and if the difference exceeded 0.05 mm, it was evaluated as × (evaluated as unusable, the same applies below).

[0049] (Evaluation of the meat pool at the base of the bottle neck) The appearance of the base of the neck of the bottle was evaluated as the appearance of the base of the neck when the bottle was viewed from the side. This evaluation was a visual sensory evaluation, and was performed in an environment of 22° C. As a result of this evaluation, if the ring was not visible at the base of the neck, it was rated as ◯, and if the ring was visible at the base of the neck, it was rated as ×.

[0050] (Evaluation of bottle grounding) The bottle's grounding was evaluated by placing the bottle on a flat table. This evaluation was performed in an environment of 22° C. As a result of this evaluation, if the bottle was placed on a flat table and the bottom of the bottle was in contact with the table without any rattling or gaps, it was rated as ◯, and if there was at least one of rattling or a gap between the bottle and the table, it was rated as ×.

[0051] (Bottle misalignment evaluation) The misalignment of the bottle was evaluated by the amount of misalignment of the gate center of the preform from the center of the bottle bottom. This evaluation was performed in an environment of 22° C. As a result of this evaluation, when the gate center of the preform was located within 5 mm from the center of the bottle bottom, it was evaluated as ◯, and when the gate center of the preform was located more than 5 mm from the center of the bottle bottom, it was evaluated as ×.

[0052] (Warmer rating: Bottom inversion rating) As part of the warmer evaluation, the condition of the bottom inversion was evaluated by filling the bottle with water at 22° C. and closing the cap, and then storing the bottle for 3 weeks in a bottle warmer (manufactured by Nippon Heater Kiki, TW75-C3) with the heater output adjusted to keep the liquid temperature at 70° C. As a result of this evaluation, if the bottle bottom did not invert (buckle), it was rated as ◯, and if the bottle bottom did invert (buckle), it was rated as ×.

[0053] (Warmer rating: neck bending rating) As part of the warmer evaluation, the neck bending evaluation was carried out by filling the bottles with water at 22°C, closing the caps, and then storing them for three weeks in a bottle warmer (manufactured by Nippon Heater Equipment, TW75-C3) with the heater output adjusted to keep the liquid temperature at 70°C. The neck bending was then evaluated. Specifically, the height of the top surface of the bottle cap was measured, and the difference between the highest and lowest points of a bottle (total height deviation) was evaluated. As a result of this evaluation, if the total height deviation was within 1 mm, it was evaluated as ◯, and if the total height deviation was more than 1 mm, it was evaluated as ×. The total height deviation is measured by measuring the bottle height from the ground surface (table) to the top of the cap at various points on the cap. The measurement is done using a height gauge, moving the bottle to measure the height from the bottle ground surface to the top of the cap at various points on the top of the cap. The total height deviation is then calculated using the following formula. Total height deviation = Bottle height at highest point - Bottle height at lowest point The reason for measuring the height of the bottle including the cap is that the bottle is filled with water and then sealed with a cap, and when the bottle is opened, the pressure inside the bottle decreases, which can change the dimensions of the bottle.

[0054] (Hot plate evaluation) For the hot plate evaluation, the bottle was filled with water at 22°C and then closed, and as a severe test for selling the bottle while it was heated, it was placed on a hot plate (Hot plate EC-1200N manufactured by AS ONE CORPORATION) with a surface temperature of 200°C, and the condition of the bottle bottom was evaluated after 60 minutes. If the bottle bottom did not invert (buckle) as a result of this evaluation, it was rated as ◯, and if the bottle bottom inverted (buckled), it was rated as ×.

[0055] FIG. 6 shows a summary of the evaluation results. For the evaluation, as shown in FIG. 6, a total of eight types of preforms, Examples 1 to 3 and Comparative Examples 1 to 5, were used to produce plastic bottles 40 (hereinafter also referred to as 280 ml bottles) as shown in FIG. 3, and the evaluation was performed. The dimensions of the preforms for each Example and Comparative Example are shown in FIG. 6. Here, the "weight of the deformed portion" in FIG. 6 refers to the weight of the portion of preform 10 excluding mouth portion 11, and is the total weight (weight of deformed portion 20) of neck portion 21, thickness changing portion 22, body portion 23, and bottom portion 24. Since the mouth portion does not deform during blow molding, the portion excluding mouth portion 11 is what predominantly affects the blow molding of the plastic bottle, and so the weight of this portion is the focus of attention.

[0056] The preforms 10 of Examples 1 to 3 and Comparative Examples 1 to 5 were all made using PET (polyethylene terephthalate). The shape of the mouth portion 11 was made to conform to the mouth standard PCO1810.

[0057] First, a comparative example in which desirable results were not obtained will be described. Comparative Example 1 From the results of Comparative Example 1, when the weight of the deformed part was 16.4 g or more (the numerical values ​​quoted in the explanation are underlined in FIG. 6), the hot plate evaluation was × for a 280 ml bottle. This is thought to be because the preform in Comparative Example 1 was less stretched than the preforms in the Examples, and the bottom part was easily crystallized and deformed by heating.

[0058] Fig. 7 is a photograph comparing the bottom of a bottle when a 280 ml bottle is blow molded with the preform of Example 1 and the bottom of a bottle when a 280 ml bottle is blow molded with the preform of Comparative Example 1. Fig. 7(a) shows the bottom of a bottle when a 280 ml bottle is blow molded with the preform of Example 1, and Fig. 7(b) shows the bottom of a bottle when a 280 ml bottle is blow molded with the preform of Comparative Example 1. The photographs in Fig. 7 were taken by cutting the bottom of each unheated bottle. In the case of Example 1 in Fig. 7(a), the range P1 considered to be thick and insufficiently stretched is narrow, whereas in the case of Comparative Example 1 in Fig. 7(b), the range P2 considered to be thick and insufficiently stretched is wide. The fact that this range P2 is wide means that the range of insufficient stretching is wide.

[0059] PET has the property of becoming more heat resistant when stretched (less likely to deform or crystallize due to heat). For this reason, a lighter preform will be able to stretch more, which will reduce the area of ​​insufficient stretching shown in the photo in Figure 7, resulting in a bottle that is more resistant to heating. However, if it is too light, the physical strength will be weak, and conversely, it will be less resistant to heating.

[0060] From the results of Comparative Example 2, when the weight of the deformed part was 10.0 g or less, the hot plate evaluation for the 280 ml bottle was ×. This is thought to be because, contrary to the results of Comparative Example 1, the weight of the deformed part was light, so the wall thickness after blow molding became too thin and the strength was insufficient.

[0061] From the results of Comparative Examples 3 and 4, when the body thickness was 2.7 mm or less, the evaluation of the meat accumulation at the base of the neck was ×. In addition, in relation to this, the evaluation of the neck bending in the warmer evaluation was ×. This is thought to be because the neck was difficult to stretch during blow molding because the difference in thickness between the neck and the body was small. Note that Comparative Example 2 has an even thinner body thickness of 2.5 mm, but the weight of the deformed part is lighter at 10.0 g for Comparative Example 2 than 11.4 for Comparative Examples 3 and 4, and is therefore thought to be the reason why the evaluation of the meat accumulation at the base of the neck was ◯. Furthermore, from the results of Comparative Examples 3 and 4, when the length L6 of deformed portion 20 was 55 mm or less, the hot plate evaluation was ×. This is thought to be because when the length L6 of deformed portion 20 is 55 mm or less, it is stretched too much in the height direction of the bottle when molded into plastic bottle 40, so that when heat is applied to plastic bottle 40, a large contraction force acts to return it to its original shape, making the bottle more susceptible to deformation by heating. When the longitudinal stretching ratio = bottle height excluding mouth part ÷ (length of deformed part - bottom thickness ÷ 2), the longitudinal stretching ratios of Comparative Examples 3 and 4 exceeded 2, and it can be said that the bottles were significantly stretched in the height direction. Therefore, the longitudinal stretching ratio is preferably 2 or less.

[0062] From the results of Comparative Example 5, when the value of bottom thickness / body thickness was 71% or less, the evaluation of the thickness deviation of the preform was ×. In addition, since the body part did not stretch uniformly during blow molding due to the large thickness deviation of the preform, the evaluation of the bottle core deviation was also ×. This is thought to be because the gate G when injection molding the preform is located at the bottom of the preform, and if this bottom thickness T5 is thinner than the body thickness T3, it becomes difficult for the molten resin to flow uniformly during injection molding.

[0063] In comparison with the above-mentioned comparative examples, various evaluation items were evaluated as ◯ for all of Examples 1, 2, and 3. Therefore, from the dimensions and weights of the preforms 10 in the above comparative examples and examples, it can be said that the preforms having the following configurations are desirable. (Desired preform shape 1) First, a desirable form of the preform (form 1) is one in which the weight of the deformed portion (the total weight of the neck portion, the weight of the thickness-changing portion, the weight of the body portion, and the weight of the bottom portion) is greater than 10.0 g and less than 16.4 g. (Desired preform shape 2) Moreover, a desirable form of the preform (form 2) is one in which the wall thickness T3 of the body portion is greater than 2.7 mm. (Desired preform shape 3) Furthermore, a desirable form of the preform (form 3) is one in which the value of bottom thickness / body thickness, which is the ratio of bottom thickness T5, which is the thickness of the thinnest tip of the bottom wall, to body thickness T3, which is the thickness of the body, is greater than 71%. (Desired preform shape 4) Furthermore, in a preferred embodiment (embodiment 4), the length L6 of the deformed portion 20 is greater than 55 mm. (Desired preform shape 5) Moreover, a longitudinal stretching ratio of 2 or less is a desirable form of the preform (form 5).

[0064] In addition to the above evaluation, when PET (polyethylene terephthalate) is used as the preform material, we investigated whether a polymerization catalyst for polyethylene terephthalate resin containing an aluminum compound or a germanium compound would be more suitable for a heating bottle. Specifically, a preform of Example 1 was produced using a PET resin containing an aluminum compound and a PET resin containing a germanium compound as a polymerization catalyst, and a hot plate evaluation was performed. In this evaluation, as an evaluation of more severe conditions, the bottle was continuously placed on the hot plate until buckling occurred for more than 60 minutes, and the time until buckling occurred was measured.

[0065] FIG. 8 is a diagram showing the evaluation results of polymerization catalysts for polyethylene terephthalate resin. The types and brands of catalysts actually used and the evaluation results are shown in Figure 8. As shown in FIG. 8, it is more preferable that the preform used as the heating bottle is made of a polyethylene terephthalate resin containing an aluminum compound as a polymerization catalyst. To find out the reason for this, the degree of crystallinity of the body of the bottle before heating was measured by X-ray diffraction, and the results are shown in Figure 8. From these results, it is believed that the good results were obtained because the polyethylene terephthalate resin containing the aluminum compound has a higher degree of crystallinity than the germanium compound. It should be noted that even a plastic bottle made of polyethylene terephthalate resin containing a germanium compound has sufficient heating properties.

[0066] By satisfying the above-described conditions of the first to fifth embodiments, a preform suitable for molding a plastic bottle for heating can be obtained. By performing blow molding using this preform, a lightweight plastic bottle for heating that has good heating properties can be produced.

[0067] The bottle is not limited to 280 ml having a circumferential groove as exemplified in the above embodiment, but may be, for example, a bottle having a pressure absorbing panel, or a bottle having no grooves, pressure absorbing panels, etc. The capacity of the bottle is also not limited to 280 ml, but may be 140 ml or more and 420 ml or less, preferably 190 ml or more and 350 ml or less.

[0068] The present disclosure is not limited to the above-described embodiments. [Explanation of symbols]

[0069] 10 Preform 11 Mouth 12 Mouth body 13 Threaded part 14 Support Ring 15 Opening 21 Neck 21a Exterior 21b Inside 22 Thickness change area 22a Exterior 22b Inside 23 Torso 23a Exterior 23b Inside 24 Bottom 24a Exterior 24b Inside 40 Plastic Bottles 41 Mouth 42 Main body 42a Shoulder 42b Torso 42c bottom 42d bulge 42e truncated cone surface 42f flat surface 43 Circumferential groove 45 Neck 46 Threaded part 47 Support Ring G Gate

Claims

1. In preforms for heated plastic bottles, a mouth portion having a support ring; A neck portion connected to the mouth portion; a thickness changing portion connected to the neck portion and having a thickness changing portion that decreases in diameter as it moves away from the neck portion; a body portion connected to the thickness changing portion, the body portion having an outer diameter smaller than that of the neck portion and a substantially uniform thickness; A bottom portion provided on an opposite side of the body portion from the thickness changing portion; Equipped with The total weight of the neck portion, the thickness changing portion, the body portion, and the bottom portion is greater than 10.0 g and less than 16.4 g; The wall thickness of the body portion is greater than 2.7 mm, A preform, in which the value of bottom thickness / body thickness is greater than 71%, when the thickness of the thinnest tip of the bottom portion is taken as the bottom thickness.

2. The preform according to claim 1, A preform, wherein the length from the tip of the bottom portion to the boundary between the neck portion and the mouth portion is greater than 55 mm.

3. The preform according to claim 1 or 2, The preform is made of polyethylene terephthalate resin.

4. The preform according to claim 3, The preform contains an aluminum compound as a polymerization catalyst for the polyethylene terephthalate resin.

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